Hydraulic apparatus

Abstract

A hydraulic apparatus for changing flow rate by displacing the flow rate changing member of a variable displacement hydraulic pump accommodated in a casing for eliminating any surplus and leaked oil and diminished kinetic energy loss comprises an actuator, a flow rate control valve, a resilient member accommodated in the casing to urge the flow rate changing member toward the direction where the flow rate of the hydraulic pump is increased, first and second sliding members slidably received in first and second cylinder chambers, respectively, provided in the casing to urge the flow rate changing member toward the direction where the flow rate of the hydraulic pump is decreased, a first fluid conduit having one end connected with an outward port of the hydraulic pump and the other end connected with a rear port of the actuator, a second fluid conduit having one end connected with a fore port of the actuator and the other end connected with an inlet port of the hydraulic pump through the flow rate control valve, a third fluid conduit having one end connected with the second fluid conduit and the other end connected with the first cylinder chamber, and a fourth fluid conduit having one end connected with the first fluid conduit and the other end connected with the second cylinder chamber.

What is claimed is: 
     
       1. A hydraulic apparatus for changing the flow rate by displacing a flow rate changing member of a variable displacement hydraulic pump accommodated in a casing, comprising, in combination: an actuator, a first sliding member slidably received in a first cylinder chamber provided in said casing and movable in one direction to urge said flow rate changing member toward a direction where the flow rate of said hydraulic pump is decreased, a second sliding member slidably received in a second cylinder chamber provided in said casing and movable in said one direction to urge the flow rate changing member toward a direction where the flow rate of said hydraulic pump is decreased, a resilient member accommodated in said casing to resiliently urge said flow rate changing member against a resultant force of said first and second sliding member toward a direction where the flow rate of said hydraulic pump is increased, said resilient member being the only means for urging said first and second sliding members in a direction opposite to said one direction, a first fluid conduit having one end connected with an outlet port of said hydraulic pump and the other end thereof connected with a rear port of said actuator, a second fluid conduit having one end connected with a fore port of said actuator and the other end connected with a port of a pressure compensated flow control valve means for permitting pressure oil passing therethrough to be maintained constant in volume even with variations in pressure of the fluid, a third fluid conduit having one end connected with another port of said flow control valve means and the other end thereof connected with an inlet port of the hydraulic pump, a fourth fluid conduit having one end connected with said second fluid conduit and the other end connected with said first cylinder chamber, and a fifth fluid conduit having one end connected with said first fluid conduit and the other end connected with said second cylinder chamber. 
     
     
       2. A hydraulic apparatus as defined in claim 1, wherein said second cylinder chamber is formed in said first cylinder chamber in coaxial relation with said first cylinder chamber. 
     
     
       3. A hydraulic apparatus as defined in claim 1, wherein said flow rate changing member is a cam ring disposed to surround a rotor in sliding contact with vanes, each of said vanes being slidably received in each of vane bores equiangularly formed in said rotor to radially extend and to be opened at their radially outer ends. 
     
     
       4. A hydraulic apparatus as defined in claim 3, wherein said first and second sliding members are disposed around said cam ring in opposing relation with said resilient member. 
     
     
       5. A hydraulic apparatus as defined in claim 1, wherein said flow rate changing member is a swash plate which is in sliding and rolling contact with a plurality of pistons circumferentially spacedly arranged and slidably received in a cylinder block. 
     
     
       6. A hydraulic apparatus as defined in claim 5, wherein said first and second sliding members are arranged in parallel relation with each other. 
     
     
       7. A hydraulic apparatus as defined in claim 5, wherein said first and second sliding members are arranged in concentric relation with each other.